tavis



Jan. 6, 1959 I INVENITOR. JOHN R. TA v/s A TTORNE rs J. R. TAVIS Filed Dec. 14. 1954 GALVANOMETER STRUCTURE ment is not subject to the.

United- Statcs Patent 2,867,770 GALVANOMETER STRUCTURE John R. Tavis, Los Angeles, Calif., assignor, by mesne assignments, to Consolidated Electrodynamics Corpo ration, Pasadena, Calif., a corporation of California Application December 14, 1954, SerialNo..475,'129' 5 Claims. (Cl. 324-154) This invention relates to improvements in the structure of galvano-meters, and it. has particular reference to galvanometers of simplified construction and to arrangemerits for providing external electrical contacts at the lower end of galvanometers.

A typical galvanometer comprises a suspension system of a light beam at the-mirror so that deflection of the.

coil is indicated by movement of the reflected. light beam. Ordinarily, the upper end' of the suspension system is connected to an external electrical contact located, at and the lower end" of the top of the galvanometer, the suspension system is connected to the body of the galvanometer which serves as the other external electrical contact. The use of the body. of the galvanometer. as one electrical contact causes and it also requires that the galvanometer be insulated from its magnet mounting block. The insulating arrangement necessitates the use of a larger magnet structure.

than would be required if no insulation were employed.

Also, the use of an electrical contact located at the top of the galvanometer ordinarily requires a c'onnectorwhich is separate from the electrical connector which=contacts the body portion of the galvanometer.

These difiiculties are overcome inthe presentinvention by providing both of the external electrical contacts for the galvanometer at the lower end of the galvanometer and by insulating both of the external electrical contacts from the body of the galvanometer. Such an-arrangeeffects ofstray electromagnetic andelectrostatic fields, and the body of the galvanometer need not be insulated fromthe magnetlblock. Thus,--,a small magnet mounting block may be employed. A plug-in support may be employed to hold the galvanometer in the magnet structure, and it may be arranged to make electrical connections to the galvanometer when the galvanometer is plugged into the mounting structure.

Galvanometers of this type may be of simplified structure so that they are inexpensive and can be of miniature size. For example, in one embodiment of the galvanometer its external diameter was inch.

Application Serial Number 475,130, filed on the same date as the present application, discloses a similar arrangement for providing the external electrical contacts at the lower end of the galvanometer.

The invention is explained in more detail with refer: ence to the drawings, in which:

A small mirroris allixed the galvanometer .torespond to stray electromagnetic and electrostaticfields;

' parent that a setscrew may of. the galvanometer 2,857,779 i atented Jan. 6, 1959 ice Fig. 1 shows the relative proportions of an assembled galvanometer; and

, Fig. 2 is an enlarged, fragmentary, sectional view showing along line 22 of Fig. l the details of the galvanometer structure.

The galvanometer .comprisesa unitary body portion 10 of cylindrical shape. A suspension system 12 extends through the interior of the body portion of the galvanometer. The suspension system comprises an elongated coil 14 composed of fine wire, a lightweight mirror 16, and a pair of fine wires 18 and 20 which supportthe suspension system and which provide electrical connections to the coil 14. A transparent window 17 is provided in the body portion of the galvanometer adjacent the mirror.

The upper wire 18 of the suspension system is connected to a spring 22 which serves to provide tension on the suspension system. The spring is connected to a conductive member 24 having a cylindrical inner por- 7 tion and. a flanged upper portion which is located at the top-of the galvanometer.

A conductive sleeve 26 is located around the cylindricalportion of. the member 24, and an insulating sleeve 23-is located between the conductivesleeve and the body Ordinarily, it is desirable that the insulating sleeve 28- and the conductive sleeve 2d be afiixed. to the body of the galvanometer as by cementing. Itldesired, the top member. 24 may be cemented to the sleeve 26. p

The lower wire Ztl of: the suspension system is connected to a pin 30 which in turn is affixed to anexternal electrical contact member 32. The pin may be connected to the electrical contact in various. manners. In theembodiment illustrated in the drawings, the connection is efiected by solder 34. However, it will be apbe employed if the electrical contact member is f sufiicient size to permit the use ofa setscrew.

An annular-shaped electrical contact member 36 is located above the bottom contact member and it is disposed concentrically with respect to the longitudinal axis of the galvanometer. A pair of insulating members. 38 and 40 serve to insulate the two contact members from one another and also from the body of the galvanometer.

An insulated wire 42 extends through the body portion of the galvanometer and it interconnects the conductive sleeve. 26 at the top of the galvanometer and the annular-shapedelectrical contactv 36 at the lower" end of the: galvanometer so as to provide an electrical connection to. the upper end of the suspension system. Preferably, the wire 42ris bonded to the inner surface of the body of the galvanometer as by cementing at suitable locations v p The body of the galvanometer and the other conductive members may be composed of brass. Preferably, the two electrical contact members are silver plated.

Thus, both of the electrical contacts for the galvanometer are located at the lower end of the galvanometer, and both of the contacts are insulated from the body portion of the galvanometer. With such anarrangement the response of the galvanometer to stray electromagnetic and electrostatic fields is minimized. Also, the galvanometer need not be insulated from the magnet mounting structure, and the galvanometer may be employed as a plug-in unit in conjunction with a jack-type electrical connector. If desired, a stop member 44 may be located along the body of the galvanometer for controlling the distance which the galvanometer may be inserted into a connector socket.

The galvanometer is of extremely simple construction.

claims, the terms lower I vanometer refer to that end of the galvanometer which I then refer Hence, it is inexpensive. and it may be constructed in miniature form.

The electrical contact arrangement may be employed in other types of galvanometerstructure if desired. For example, in the aforesaid application, Serial Number 475,130 this type of electrical contact arrangement is employed in a more complex galvanometer structure.

For purposes of this disclosure and the following or bottom end of the galis designed to be inserted into a magnet mounting block. The terms upper or top end of the galvanometer to the opposite end of the galvanometer. that is to that end of the galvanometer which protrudes from the magnet mounting block when the galvanometer is inserted into the magnet mounting block.

I claim:

1. In a galvanometer having a body portion in which a suspension system is located, the improvement which the lower end of the suspension system and connected to and electrically insulated from the lower extremity of the body portion, an annular-shaped electrical contact afiixed to the electrical plug-in means and disposed concentrically with respect to the longitudinal axis of the galvanometer, an insulated conductive wire extending through the interior of the body portion of the galvanometer interconnecting the annular-shaped electrical contact and the upper end of the suspension system, a second electrical contact aflixed to the electrical plug-in means below the annular-shaped electrical contact and coupled to the lower end of the suspension system, and means insulating the two electrical contacts from each other and also from the body of the galvanometer, so that both of the electrical contacts for the galvanometer are located in the electrical plug-in means at the lower end of the galvanometer and are insulated from the body portion of the galvanometer.

2. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises a cylindrical electrical plug-in means holding the lower end of the suspension system and connected to and electrically insulated from the lower extremity of the body portion, an electrical contact extending around and affixed to the electrical plug-in means, a conductive wire extending through the interior of the body portion of the galvanometer interconnecting the electrical contact and the upper end of the suspension system, another electrical contact afiixed to the electrical Plug-in means below the first electrical contact and coupled to the lower end of the suspension system, and means insulating the two electrical contacts from each other and also from the body of the galvanometer.

3. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises conductive means supporting the upper end of the suspension system, means insulating the conductive means from the body of the galvanometer, a pin connected to the lower end of the suspension system, a bottom contact member disposed around the pin, an annular-shaped contact member located above the bottom contact member, means insulating the two contact members from one another and also from the body of the galvanometer, anda wire extending through the interior of the body portion of the'galvanometer and interconnectin'g the annular-shaped contact member and the conductive means at the top of the galvanometer to provide an electrical connection between the annular-shaped contact member and the upper end of the suspension system.

4. In a galvanometer having a body portion in which a suspension system is located, the improvement which comprises a spring connected to the upper end of the suspension system, a conductive cylindrical member connected to the spring and having a flange at its top, a conductive sleeve located around the cylindrical member, an insulating sleeve located between the conductive sleeve and the body of the galvanometer, a cylindrical pin connected to the lower end of the suspension system, a bottom contact member disposed around the cylindrical pin, an annular-shaped contact member located above the bottom contact member, insulating means located between the two contact members and also between the contact members and the body of the galvanometer, and an insulated conductive wire extending through the interior of the body portion of the galvanometer and interconnecting the annular contact member and the conductive sleeve at the'top of the galvanometer, so that both of the electrical contacts for the galvanometer are located at the lower end of the galvanometer and are insulated from the body portion of the galvanometer.

5. In agalvanometer having a body portion in which a suspension system is located, the improvement which comprises a spring connected to the upper end of the suspension system, a conductive cylindrical member connected to the spring and having a flange at its top, a conductive sleeve located around the cylindrical member, an insulating sleeve located between the conductive sleeve and the body of the galvanometer, a cylindrical pin connected to the lower end of the suspension system, a bottom electrical contact member disposed around the cylindrical pin, solder means afiixing the cylindrical pin to the bottom contact member, an annular-shaped electrical contact member located above the bottom contact member, insulating means located between the two contact members and also between the contact members and the body of the galvanometer, and an insulatedwire extendingthrough the interior of the body portion of the galvanometer and interconnecting the annular contact member and the conductive sleeve at the top of the galvanometer, so that both of the electrical contacts for the galvanometer are located at the lower end of the galvanometer and are insulated from the body portion of the galvanometer.

References Cited in the file of this patent UNITED STATES PATENTS 

